Single microstructure lens, systems and methods

ABSTRACT

Systems and methods for providing enhanced image quality across a wide and extended range of foci encompass vision treatment techniques and ophthalmic lenses such as contact lenses and intraocular lenses (IOLs). Exemplary IOL optics can include a circular surface structure which acts as a diffractive or phase shifting profile. In some cases, a single ring IOL includes an anterior face and a posterior face, where a profile can be imposed on the anterior or posterior surface or face. The profile can have an inner portion such as a microstructure or central echelette, and an outer portion. Between the inner portion and the outer portion, there may be a transition zone that connects the inner and outer portions.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.application Ser. No. 14/589,197, filed Jan. 5, 2015, which is acontinuation application and claims priority to U.S. application Ser.No. 13/872,784, entitled “Single Microstructure Lens, Systems andMethods”, filed on Apr. 29, 2013 and issued as U.S. Pat. No. 8,926,092,which is a continuation application and claims priority to U.S.application Ser. No. 12/971,506, entitled “Single Microstructure Lens,Systems and Methods”, filed on Dec. 17, 2010 and issued as U.S. Pat. No.8,430,508, which claims priority under 35 U.S.C §119(e) to provisionalapplication No. 61/288,255 filed on Dec. 18, 2009, the entire contentsof which are incorporated herein by reference. This application isrelated to the following applications which were filed concurrentlyherewith: Limited Echelette Lens, Systems And Methods, U.S. patentapplication Ser. No. 12/971,607, filed on Dec. 17, 2010; OphthalmicLens, Systems And Methods With Angular Varying Phase Delay, U.S. patentapplication Ser. No. 12/971,889, filed on Dec. 17, 2010; and OphthalmicLens, Systems And Methods Having At Least One Rotationally AsymmetricDiffractive Structure, U.S. Patent Application No. 61/424,433, filed onDec. 17, 2010. The entire contents of these three applications are alsoincorporated herein by reference. This application is also related tothe following U.S. patent application Ser. Nos. 61/047,699 and12/109,251, both filed on Apr. 24, 2008; Ser. No. 12/429,155 filed onApr. 23, 2009; Ser. No. 12/372,573 filed on Feb. 17, 2009; Ser. No.12/197,249 filed on Aug. 23, 2008; Ser. No. 12/120,201 filed on Apr. 13,2008, and Ser. No. 12/771,550 filed on Apr. 30, 2010.

BACKGROUND OF THE INVENTION

Embodiments of the present invention relate to vision treatmenttechniques and in particular, to ophthalmic lenses such as, for example,contact lenses, corneal inlays or onlays, or intraocular lenses (IOLs)including, for example, phakic IOLs and piggyback IOLs (i.e. IOLsimplanted in an eye already having an IOL).

Presbyopia is a condition that affects the accommodation properties ofthe eye. As objects move closer to a young, properly functioning eye,the effects of ciliary muscle contraction and zonular relaxation allowthe lens of the eye to change shape, and thus increase its optical powerand ability to focus at near distances. This accommodation can allow theeye to focus and refocus between near and far objects.

Presbyopia normally develops as a person ages, and is associated with anatural progressive loss of accommodation. The presbyopic eye oftenloses the ability to rapidly and easily refocus on objects at varyingdistances. The effects of presbyopia usually become noticeable after theage of 45 years. By the age of 65 years, the crystalline lens has oftenlost almost all elastic properties and has only a limited ability tochange shape.

Along with reductions in accommodation of the eye, age may also induceclouding of the lens due to the formation of a cataract. A cataract mayform in the hard central nucleus of the lens, in the softer peripheralcortical portion of the lens, or at the back of the lens. Cataracts canbe treated by the replacement of the cloudy natural lens with anartificial lens. An artificial lens replaces the natural lens in theeye, with the artificial lens often being referred to as an intraocularlens or “IOL”.

Monofocal IOLs are intended to provide vision correction at one distanceonly, usually the far focus. Predicting the most appropriate IOL powerfor implantation has limited accuracy, and an inappropriate IOL powercan leave patients with residual refraction errors following surgery.Accordingly, it may be necessary for a patient who has received an IOLimplant to also wear spectacles to achieve good far vision. At the veryleast, since a monofocal IOL provides vision treatment at only onedistance and since the typical correction is for far distance,spectacles are usually needed for good near and sometimes intermediatevision. The term “near vision” generally corresponds to vision providedwhen objects are at a distance from the subject eye of between about 1to 2 feet are substantially in focus on the retina of the eye. The term“distant vision” generally corresponds to vision provided when objectsat a distance of at least about 6 feet or greater are substantially infocus on the retina of the eye. The term “intermediate vision”corresponds to vision provided when objects at a distance of about 2feet to about 5 feet from the subject eye are substantially in focus onthe retina of the eye.

There have been various attempts to address limitations associated withmonofocal IOLs. For example, multifocal IOLs have been proposed thatdeliver, in principle, two foci, one near and one far, optionally withsome degree of intermediate focus. Such multifocal, or bifocal, IOLs areintended to provide good vision at two distances, and include bothrefractive and diffractive multifocal IOLs. In some instances, amultifocal IOL intended to correct vision at two distances may provide anear add power of about 3.0 or 4.0 diopters.

Multifocal IOLs may, for example, rely on a diffractive optical surfaceto direct portions of the light energy toward differing focal distances,thereby allowing the patient to clearly see both near and far objects.Multifocal ophthalmic lenses (including contact lenses or the like) havealso been proposed for treatment of presbyopia without removal of thenatural crystalline lens. Diffractive optical surfaces, either monofocalor multifocal, may also be configured to provide reduced chromaticaberration.

Diffractive monofocal and multifocal lenses can make use of a materialhaving a given refractive index and a surface curvature which provide arefractive power. Diffractive lenses have a diffractive profile whichconfers the lens with a diffractive power that contributes to theoverall optical power of the lens. The diffractive profile is typicallycharacterized by a number of diffractive zones. When used for ophthalmiclenses these zones are typically annular lens zones, or echelettes,spaced about the optical axis of the lens. Each echelette may be definedby an optical zone, a transition zone between the optical zone and anoptical zone of an adjacent echelette, and an echelette geometry. Theechelette geometry includes an inner and outer diameter and a shape orslope of the optical zone, a height or step height, and a shape of thetransition zone. The surface area or diameter of the echelettes largelydetermines the diffractive power(s) of the lens and the step height ofthe transition between echelettes largely determines the lightdistribution between the different add powers. Together, theseechelettes form a diffractive profile.

A multifocal diffractive profile of the lens may be used to mitigatepresbyopia by providing two or more optical powers; for example, one fornear vision and one for far vision. The lenses may also take the form ofan intraocular lens placed within the capsular bag of the eye, replacingthe original lens, or placed in front of the natural crystalline lens.The lenses may also be in the form of a contact lens, most commonly abifocal contact lens, or in any other form mentioned herein.

Although multifocal ophthalmic lenses lead to improved quality of visionfor many patients, additional improvements would be beneficial. Forexample, some pseudophakic patients experience undesirable visualeffects (dysphotopsia), e.g. glare or halos. Halos may arise when lightfrom the unused focal image creates an out-of-focus image that issuperimposed on the used focal image. For example, if light from adistant point source is imaged onto the retina by the distant focus of abifocal IOL, the near focus of the IOL will simultaneously superimpose adefocused image on top of the image formed by the distant focus. Thisdefocused image may manifest itself in the form of a ring of lightsurrounding the in-focus image, and is referred to as a halo. Anotherarea of improvement revolves around the typical bifocality of multifocallenses. Since multifocal ophthalmic lenses typically provide for nearand far vision, intermediate vision may be compromised.

A lens with an extended depth of focus may thus provide certain patientsthe benefits of good vision at a range of distances, while havingreduced or no dysphotopsia. Various techniques for extending the depthof focus of an IOL have been proposed. For example, some approaches arebased on a bulls-eye refractive principle, and involve a central zonewith a slightly increased power. Other techniques include an asphere orinclude refractive zones with different refractive zonal powers.

Although certain proposed treatments may provide some benefit topatients in need thereof, further advances would be desirable. Forexample, it would be desirable to provide improved IOL systems andmethods that confer enhanced image quality across a wide and extendedrange of foci without dysphotopsia. Embodiments of the present inventionprovide solutions that address the problems described above, and henceprovide answers to at least some of these outstanding needs.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention generally provide improved lensesand imaging techniques. Exemplary embodiments provide improvedophthalmic lenses (such as, for example, contact lenses, corneal inlaysor onlays, or intraocular lenses (IOLs) including, for example, phakicIOLs and piggyback IOLs) and associated methods for their design anduse.

Embodiments of the present invention encompass IOL optics having asingular circular surface structure, which acts as a phase shiftingprofile. The profile is designed such that it increases the depth offocus of the pseudophakic eye, where the natural crystalline lens of theeye is substituted with a synthetic lens. Such a singular IOL techniquesuppresses the distinct bifocality associated with traditionalmultifocal IOLs which have many diffractive rings. Consequently,dysphotopsia (e.g., halo effects) associated with traditional multifocalIOLs can be alleviated by lenses according to embodiments of the presentinvention.

An exemplary single ring IOL includes an anterior face and a posteriorface. A profile can be imposed on the anterior or posterior surface orface. The profile can have an inner portion and an outer portion. Theinner portion typically presents a parabolic curved shape. The innerportion may also be referred to as a microstructure, an isolatedechelette, or a central echelette. Between the inner portion and theouter portion, there may be a transition zone that connects the innerand outer portions.

In addition to parabolic shapes, the central echelette can have any of avariety of shapes including hyperbolic, spherical, aspheric, andsinusoidal. The transition between the inner and outer portions of theechelette can be a sharp transition or it can be a smooth transition.

The surface of the outer portion at the outside of the microstructurecan have any spherical or aspherical shape. The shape of the outerportion can be optimized for having the desired optical performance fora range of pupil sizes. The desired optical performance can be based onelements such as the depth of focus, the optical quality in the farfocus, and the change in best focus (or far focus) position as afunction of the pupil size. Optimization rules may be applied as if theshape were a refractive monofocal IOL, or a refractive IOL having anextended depth of focus, or a refractive design that corrects ormodifies the ocular spherical aberration. Specific designs can be madein which the interplay between the central echelette and the outer zoneis incorporated in the design or optimization. The techniques describedherein are well suited for implementation with any of a variety ofophthalmic lenses, including IOLs, corneal inlays or onlays, and/orcontact lenses.

In one aspect, embodiments of the present invention encompass ophthalmiclens systems and methods for treating an eye of a patient. An exemplarylens may include an anterior face with an anterior refractive profileand a posterior face with a posterior refractive profile. The faces maybe disposed about an optical axis. The lens may also include adiffractive profile imposed on the anterior refractive profile, on theposterior refractive profile, or on both. In an exemplary embodiment, adiffractive profile may include no more than one echelette. Optionally,the echelette can be disposed within a central zone of the lens.Relatedly, the echelette may be positioned as an annulus surrounding acentral refractive zone of the lens. In some cases, the lens includes aperipheral zone that surrounds the echelette or annular ring. Theechelette may be characterized by a constant phase shift.

According to some embodiments, an ophthalmic lens can include anechelette that is characterized by a parabolic curve. An echelette canhave a diameter within a range from about 1 mm to about 4 mm. Forexample, an echelette may have a diameter of about 1.5 mm. In somecases, an echelette can have a diameter within a range from about 1.0 mmto about 5.0 mm. The echelette can have a surface area that is between 1and 7 mm². Preferably, the echelette can have a surface area that isbetween 1.5 and 4 mm². For example, the echelette may have a surfacearea that is 2.3 mm².

Lens embodiments may include a peripheral portion characterized by aspherical curve or an aspherical curve. In some cases, the peripheralportion can be refractive. A lens may include a peripheral portionhaving an outer diameter within a range from about 4 mm to about 7 mm.For example, a lens may include a peripheral portion having an outerdiameter of about 5 mm.

A lens may include a transition characterized by a step height having avalue within a range from about 0.5 μm and about 4 μm. According to someembodiments, a transition can be characterized by a step height having avalue within a range of about 1.5 μm and 2.5 μm. According to someembodiments, a transition can be characterized by a step height having avalue of about 1.7 μm. In other embodiments, the step height may have avalue of about 2.0 μm.

The extended depth of focus may be based on a relative threshold over arange of foci. For instance, image quality may be presented by thevolume under the white-light MTF curve, as a percentage of the volumeunder the white-light diffraction limited MTF (“MTF volume”). In somecases, a lens can provide an MTF volume of at least about 35% throughouta continuous range from about −1.25D to about 0.25D for a 2.0 mm pupil.In other words, a lens can provide an MTF volume of at least 35% over acontinuous range of at least about 1.5D. Certain embodiments of thepresent invention provide for an MTF volume of at least 35% over acontinuous range of at least about 0.75D. Other embodiments can providean MTF volume of at least 35% over a continuous range of at least about1.0D. More preferably, embodiments can provide an MTF volume of at least35% over a continuous range of at least 1.25D. In some cases, a lens canprovide an MTF at 50 cycles per millimeter of at least 15 over acontinuous range of at least about 1.5D. Certain embodiments provide anMTF at 50 cycles per millimeter of at least 15 over a continuous rangeof at least 1.0D. In other cases, a lens can provide an MTF at 100cycles per millimeter of at least 7 over a range of at least about 1.8D.Certain embodiments provide an MTF at 100 cycles per millimeter of atleast 7 over a continuous range of at least 1.5D.

In some cases, a diffractive profile can be characterized by a designwavelength, and a lens can include a transition characterized by a stepheight producing a phase shift between about 0.25 and about 1 times thedesign wavelength. In some cases, a diffractive profile can becharacterized by a design wavelength, and the lens can include atransition characterized by a step height producing a phase shiftbetween about 0.15 and about 2 times the design wavelength. According tosome embodiments the lens may include a transition characterized by astep height producing a phase shift of about 0.5. In other embodiments,the lens may include a transition characterized by a step height ofabout 0.4.

In another aspect, embodiments of the present invention encompasssystems and methods that involve an ophthalmic lens having a diffractiveprimary zone that presents a base diffractive surface having a purelyoptical function, and a refractive peripheral zone that surrounds thediffractive primary zone. An ophthalmic lens may also include atransition zone that physically connects the diffractive primary zonewith the refractive peripheral zone. The transition zone may optionallyprovide optical characteristics.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be had to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view of an eye with a multifocal refractiveintraocular lens.

FIG. 1B is a cross-sectional view of an eye having an implantedmultifocal diffractive intraocular lens.

FIG. 2A is a front view of a diffractive multifocal ophthalmic lens.

FIG. 2B is a cross-sectional view of the lens of FIG. 2A.

FIGS. 3A-3B are graphical representations of a portion of thediffractive profile of a conventional diffractive multifocal lens.

FIG. 4 shows aspects of a single microstructure lens according toembodiments of the present invention.

FIGS. 4A-4B illustrate aspects of a lens profile according toembodiments of the present invention.

FIG. 4C depicts aspects of a profile of a lens according to embodimentsof the present invention.

FIG. 4D shows aspects of a single microstructure lens according toembodiments of the present invention.

FIG. 5 illustrates aspects of an optical system layout of a schematiceye according to embodiments of the present invention.

FIGS. 5A-5C show aspects of reference designs according to embodimentsof the present invention.

FIGS. 6A-6D illustrate aspects of design profile evaluation according toembodiments of the present invention.

FIGS. 7A-7D illustrate aspects of design profile evaluation according toembodiments of the present invention.

FIGS. 8A-8D illustrate aspects of design profile evaluation according toembodiments of the present invention.

FIGS. 9A-9D illustrate aspects of design profile evaluation according toembodiments of the present invention.

FIGS. 10A-10C illustrate aspects of design profile evaluation accordingto embodiments of the present invention.

FIGS. 11A-11C illustrate aspects of design profile evaluation accordingto embodiments of the present invention.

FIGS. 12A-12C illustrate aspects of design profile evaluation accordingto embodiments of the present invention.

FIGS. 13A-13C illustrate aspects of design profile evaluation accordingto embodiments of the present invention.

FIGS. 14A-14C illustrate aspects of design profile evaluation accordingto embodiments of the present invention.

FIGS. 15A-15C illustrate aspects of design profile evaluation accordingto embodiments of the present invention.

FIGS. 16A-16C illustrate aspects of design profile evaluation accordingto embodiments of the present invention.

FIGS. 17A-17C illustrate aspects of design profile evaluation accordingto embodiments of the present invention.

FIGS. 18A-18C show aspects of designs according to embodiments of thepresent invention.

FIGS. 19A and 19B show aspects of measured defocus curves according toembodiments of the present invention.

FIGS. 20A-20C show aspects of measured defocus curves according toembodiments of the present invention.

FIG. 21 depicts aspects of a diffractive single ring IOL according toembodiments of the present invention.

FIG. 22 depicts aspects of a diffractive single ring IOL according toembodiments of the present invention.

FIGS. 23A-1 to 23D-2 show aspects of dysphotopsia performance accordingto embodiments of the present invention.

FIG. 24 shows aspects of dysphotopsia performance according toembodiments of the present invention.

For illustration purposes, the profile geometries shown in certainaforementioned figures were not drawn exactly to scale. The heights ofthe profiles shown in the figures are generally on the order of about0.5 μm to about 8.0 μm although the heights may vary depending onfactors such as the amount of correction needed by the patient, therefractive index of the lens material and surrounding medium, and thedesired phase shift/delay.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the figures and descriptions of the presentinvention have been simplified to illustrate elements that are relevantfor a clear understanding of the present invention, while eliminating,for the purpose of clarity and brevity, many other elements found intypical ophthalmic lenses, implantable optic apparatuses, systems andmethods. Those of ordinary skill in the art may thus recognize thatother elements and/or steps are desirable and/or required inimplementing the present invention. However, because such elements andsteps are well known in the art, and because they do not facilitate abetter understanding of the present invention, a discussion of suchelements and steps is not provided herein. The disclosure herein isdirected to all such variations and modifications to the disclosedelements and methods known to those skilled in the art.

Embodiments of the present invention encompass systems and methods thatprovide improved image quality over an extended range of focal points orfoci. Systems and methods disclosed herein can encompass variousophthalmic lenses such as, for example, contact lenses, intraocularlenses, spectacle lenses, and corneal inlays or onlays. Exemplaryembodiments include ophthalmic lenses having an extended depth of focus,as compared to conventional monofocal lenses, and reduced dysphotopsiaas compared to conventional multifocal ophthalmic lenses. In some cases,such techniques involve an IOL approach that includes a single ring, orechelette, and typically involves an expanded depth of focus.Advantageously, such approaches can provide a patient with good distancevision, as well as good vision at intermediate distances withoutdysphotopsia.

Embodiments of the present invention generally provide improved lensesand imaging systems and may be incorporated into any system in which alens with an extended depth of focus may be advantageous, such ascamera/video lenses, including those used for surveillance or forsurgical procedures, as well as for cameras in mobile phones or otherrelated devices.

Embodiments of the invention may find their most immediate use in theform of improved ophthalmic devices, systems, and methods. Exemplaryembodiments of the present invention provide improved ophthalmic lenses(including, for example contact lenses, intraocular lenses (IOLs),corneal implants and the like) and associated methods for their designand use. Embodiments of the present invention may be used with monofocaldiffractive or refractive lenses, bifocal diffractive or refractivelenses, and multifocal diffractive or refractive lenses, e.g.embodiments of the present invention could be added to the oppositesurface of multifocal IOLs, e.g. TECNIS Multifocal, REZOOM, or RESTORIOLs. In other words, an extended depth of focus feature may be addedto, for example, the opposite surface of a diffractive or refractivemultifocal embodiment. In addition, an extended depth of focus featuremay be added to, for example, a toric IOL, an IOL that modifies ocularspherical and/or chromatic aberration, and/or an accommodating IOL. Ingeneral, an extended depth of focus feature may be added to an IOL thatmodifies ocular aberrations.

Reading is often done in bright light conditions in which the pupil issmall. In contrast, night-time driving is done in low light conditionsin which the pupil is large. Embodiments of the present inventionencompass lenses that relatively emphasize intermediate or near visionfor small pupil sizes, while also relatively emphasizing far vision forlarge pupil sizes. In some such ophthalmic lenses, a greater proportionof light energy may be transmitted to the far focus from a peripheralportion of the lens to accommodate for low light, far viewing conditionssuch as night time driving; the near or intermediate focus may receiverelatively more light energy than a central portion of the diffractiveprofile—for reading or computer work for example and/or to provide depthof focus and intermediate or near viewing under low light readingconditions as in for example reading restaurant menus.

FIG. 1A is a cross-sectional view of an eye E fit with a multifocal IOL11. As shown, multifocal IOL 11 may, for example, comprise a bifocalIOL. Multifocal IOL 11 receives light from at least a portion of cornea12 at the front of eye E and is generally centered about the opticalaxis of eye E. For ease of reference, FIGS. 1A and 1B do not disclosethe refractive properties of other parts of the eye, such as the cornealsurfaces. Only the refractive and/or diffractive properties of themultifocal IOL 11 are illustrated.

Each major face of lens 11, including the anterior (front) surface andposterior (back) surface, generally has a refractive profile, e.g.biconvex, plano-convex, plano-concave, meniscus, etc. The two surfacestogether, in relation to the properties of the surrounding aqueoushumor, cornea, and other optical components of the overall opticalsystem, define the effects of the lens 11 on the imaging performance byeye E. Conventional, monofocal IOLs have a refractive power based on therefractive index of the material from which the lens is made, and alsoon the curvature or shape of the front and rear surfaces or faces of thelens.

In a young healthy eye, contraction and relaxation of ciliary muscles 17surrounding the capsular bag 14 contribute to accommodation of the eye,the process by which the eye increases optical power to maintain focuson objects as they move closer. As a person ages, the degree ofaccommodation decreases and presbyopia, the diminished ability to focuson near objects, often results. A patient may therefore conventionallyuse corrective optics having two optical powers, one for near vision andone for far vision, as provided by multifocal IOL 11.

Multifocal lenses may optionally also make special use of the refractiveproperties of the lens. Such lenses generally include different powersin different regions of the lens so as to mitigate the effects ofpresbyopia. For example, as shown in FIG. 1A, a perimeter region ofrefractive multifocal lens 11 may have a power which is suitable forviewing at far viewing distances. The same refractive multifocal lens 11may also include an inner region having a higher surface curvature and agenerally higher overall power (sometimes referred to as a positive addpower) suitable for viewing at near distances.

Rather than relying entirely on the refractive properties of the lens,multifocal diffractive IOLs or contact lenses can also have adiffractive power, as illustrated by the IOL 18 shown in FIG. 1B. Thediffractive power can, for example, comprise positive or negative addpower, and that add power may be a significant (or even the primary)contributor to the overall optical power of the lens. The diffractivepower is conferred by a plurality of concentric diffractive zones whichform a diffractive profile. The diffractive profile may either beimposed on the anterior face or posterior face or both.

The diffractive profile of a diffractive multifocal lens directsincoming light into a number of diffraction orders. As light 13 entersfrom the front of the eye, the multifocal lens 18 directs light 13 toform a far field focus 15 a on retina 16 for viewing distant objects anda near field focus 15 b for viewing objects close to the eye. Dependingon the distance from the source of light 13, the focus on retina 16 maybe the near field focus 15 b instead. Typically, far field focus 15 a isassociated with 0^(th) diffractive order and near field focus 15 b isassociated with the 1^(st) diffractive order, although other orders maybe used as well.

Multifocal ophthalmic lens 18 typically distributes the majority oflight energy into the two viewing orders, often with the goal ofsplitting imaging light energy about evenly (50%:50%), one viewing ordercorresponding to far vision and one viewing order corresponding to nearvision, although typically, some fraction goes to non-viewing orders.

In some embodiments, corrective optics may be provided by phakic IOLs,which can be used to treat patients while leaving the natural lens inplace. Phakic IOLs may be angle supported, iris supported, or sulcussupported. The phakic IOL can be placed over the natural crystallinelens or piggy-backed over another IOL. It is also envisioned that thepresent invention may be applied to inlays, onlays, accommodating IOLs,spectacles, and even laser vision correction

FIGS. 2A and 2B show aspects of a standard diffractive multifocal lens20. Multifocal lens 20 may have certain optical properties that aregenerally similar to those of multifocal IOL 18 described above.Multifocal lens 20 has an anterior lens face 21 and a posterior lensface 22 disposed about optical axis 24. The faces 21, 22 of lens 20typically define a clear aperture 25. As used herein, the term “clearaperture” means the opening of a lens or optic that restricts the extentof a bundle of light rays from a distant source that can be imaged orfocused by the lens or optic. The clear aperture is usually circular andis specified by its diameter, and is sometimes equal to the fulldiameter of the optic.

When fitted onto the eye of a subject or patient, the optical axis oflens 20 is generally aligned with the optical axis of eye E. Thecurvature of lens 20 gives lens 20 an anterior refractive profile and aposterior refractive profile. Although a diffractive profile may also beimposed on either anterior face 21 and posterior face 22 or both, FIG.2B shows posterior face 22 with a diffractive profile. The diffractiveprofile is characterized by a plurality of annular optical zones orechelettes 23 spaced about optical axis 24. While analytical opticstheory generally assumes an infinite number of echelettes, a standardmultifocal diffractive IOL typically has at least 9 echelettes, and mayhave over 30 echelettes. For the sake of clarity, FIG. 2B shows only 4echelettes. Typically, an IOL is biconvex, or possibly plano-convex, orconvex-concave, although an IOL could be plano-plano or other refractivesurface combinations.

FIGS. 3A and 3B are graphical representations of a portion of a typicaldiffractive profile of a multifocal lens. While the graph shows only 3full echelettes, typical diffractive lenses extend to at least 9echelettes to over 32 echelettes. In FIG. 3A, the height of the surfacerelief profile (from a plane perpendicular to the light rays) of eachpoint on the echelette surface is plotted against the square of theradial distance (r² or φ from the optical axis of the lens. Inmultifocal lenses, each echelette 23 may have a diameter or distancefrom the optical axis which is often proportional to √n, n being thenumber of the echelette 23 as counted from optical axis 24. Eachechelette has a characteristic optical zone 30 and transition zone 31.Optical zone 30 typically has a shape or downward slope that may belinear when plotted against ρ as shown in FIG. 3A. When plotted againstradius r, optical zone 30 has a shape or downward slope that isparabolic as shown in FIG. 3B. As for the typical diffractive multifocallens, as shown here, all echelettes have the same surface area. The areaof echelettes 23 determines the add power of lens 20, and, as area andradii are correlated, the add power is also related to the radii of theechelettes.

As shown in FIGS. 3A and 3B, transition zone 31 between adjacentechelettes is sharp and discontinuous. The height of the lens facesharply transitions from sloping steadily downwards to steppingvertically upwards, and the transitions abruptly back to slopingsteadily downwards again. In doing so, echelettes 23 also have acharacteristic step height 32 defined by the distance between the lowestpoint and height point of the echelette. Hence, the slope (or firstderivative) and/or the curvature (second derivative) of the diffractivesurface are discontinuous adjacent the transitions.

Finite Microstructure

FIG. 4 provides a graphical representation of a cross section of asingle microstructure lens profile 100, according to embodiments of thepresent invention. Only half of the lens is shown, although since thelens is rotationally symmetric, the other half is a mirror image thatcomplements the lens at the left side of FIG. 4. Profile 100 of thesingle ring surface includes an inner portion or single ring 110, a stepor transition 120, and an outer portion 130. Inner portion 110 extendsbetween a central location 170 of profile 100 and transition 120, andouter portion 130 extends between transition 120 and a peripherallocation 180 of profile 100. Central location 170 is typically disposedat the optical axis (although in certain embodiments it may beoffset—for example to match the pupil center or an offset eye axis,etc.). In this specific example, transition 120 is disposed at adistance of about 1.5 mm from the optical axis, and peripheral location180 is disposed at the diameter of the clear aperture of the lens, hereat a distance of about 3.0 mm from the optical axis. In some cases,transition 120 can be disposed at a distance from the optical axis thatis within a range from about 0.5 mm to about 2.0 mm, and peripherallocation 180 can be disposed at a distance from the optical axis that iswithin a range from about 2.0 to about 3.5 mm, or bigger (for example,for contact lenses, the ranges would be approximately 15% larger due tothe optically more powerful position of contact lens compared to an IOL;those skilled in the art would appropriately scale certain dimensionsdepending on the application).

As shown in FIG. 4, the surface height or sag (d) from a reference planeperpendicular to the optical axis, of each point on the lens profile isplotted against the radial distance (r) from the optical axis of thelens. As shown here, the value of displacement or total sag (d) can havea value within a range from about 0 mm to about 0.07 mm. The total sagcan depend on the refractive shape of the surface and can have a value,for an IOL, of typically between 0 mm and about 2 mm, or to about minus2 mm, in cases where the surface is concave.

Inner Portion

Inner portion or echelette 110 includes a center 110 a and a peripheraledge 110 b. At center or central section 110 a of inner portion 110, thesag (d) of inner portion 110 is substantially equivalent to thedisplacement or sag (d) of peripheral curve 160. At peripheral edge 110b, the sag (d) of inner portion 110 is substantially equivalent to thesag (d) of diffractive base curve 140. Where radial distance (r) iszero, sag (d) of inner portion 110 is equivalent to the value of theperipheral curve 160. The value of sag (d) between radial distance zeroand radial distance at the peripheral edge 110 b, for example at 1.5 mm,gradually and smoothly changes from the value of peripheral curve 160(at r=0) to diffractive base curve 140 (at r=1.5 mm) in a parabolicfashion. As shown here, inner portion 110 can present a parabolic shape,for example as described in Equation 4a of Cohen, Applied Optics, 31:19,pp. 3750-3754 (1992), incorporated herein by reference. It is understoodthat in some instances, inner portion 110 may present any of a varietyof shapes or profiles, including hyperbolic shapes, spherical shapes,aspheric, and sinusoidal shapes. The shape of inner portion 110 can beimposed on a refractive shape.

Transition

At the peripheral edge 110 b, where the radial distance (r) is 1.5 mm,the value of sag (d) steps or changes from the value of diffractive basecurve 140 to the value of peripheral curve 160. Where radial distance(r) corresponds to transition 120, sag (d) of inner portion 110 isequivalent to the value of the diffractive base curve 140. Relatedly,the displacement of the profile 100 approaches that of the peripheralcurve 160 as the radial distance increases from a value of zero to avalue of about 1.5 mm. The value of the offset can be determined alongthe vertical axis. The offset value may be selected depending on theamount of phase delay. According to one embodiment, the inner portion110 and the outer portion 130 may not end up at the same vertical heightat position 110 b/130 a. One way to connect these two endpoints is byusing a straight vertical line. As shown here, the diffractivetransition step provides a sharp step in the profile. In some cases thetransition is characterized by a step height having a value within arange from about 0.5 μm and about 4 μm. According to some embodiments, atransition can be characterized by a step height having a value within arange of about 1.5 μm and 2.5 μm.

Outer Portion

Outer portion 130 includes an inner or central edge 130 a and aperipheral edge 130 b. At inner edge 130 a, the sag (d) of outer portion130 is substantially equivalent to the sag (d) of peripheral curve 160.At peripheral edge 130 b, the sag (d) of outer portion 130 remainssubstantially equivalent to the sag (d) of peripheral curve 160. Thevalue of sag (d) for the outer portion 130 of profile 100 between radialdistance 1.5 mm and radial distance 3.0 mm is equivalent to the value ofperipheral curve 160. The sag of the profile 100 and the peripheralcurve 160 are approximately equivalent between radial distance values of1.5 mm and 3.0 mm. As shown here, outer portion 130 can provide a normalspherical or aspherical curve, such as a Tecnis aspheric surface, whichcorrects or treats the ocular spherical aberration. For a more detaileddescription of the Tecnis IOL see U.S. Pat. No. 7,615,073, the contentof which is incorporated herein by reference. Virtually any asphericprofile may be used. In some cases, a Tecnis profile, or an asphericalsurface that modifies, reduces, or increases the ocular sphericalaberration, can be used. A refractive multifocal surface can also beused, or a refractive aspherical or zonal refractive surface thatextends the depth of focus. The diffractive multifocal may be on theopposite side.

As compared with lenses having a plurality of echelettes, and where stepheight increases or decreases as radial distance increases, embodimentsof the present invention encompass lens configurations where such stepconfigurations are absent.

The size of the human pupil varies with illumination. In bright lightthe pupil is small, and in dim or low light conditions the pupil islarge. In addition, the size of the human pupil varies withaccommodative effort. Without accommodative effort, the pupil is largerthan with accommodative effort. Hence, for a smaller pupil, it may bedesirable to provide a design that places a relative emphasis onintermediate or near vision. For a larger pupil, it may be desirable toprovide a design that places a relative emphasis on far vision. Suchconsiderations may affect IOL design.

The condition of dysphotopsia (e.g. halos) that is present formultifocal lenses is observed to be dominated by separation of two foci.Accordingly, pursuant to exemplary embodiments of the present invention,the lens may include only a single microstructure ring, so that lightseparation between distinct foci is not complete, as compared todiffractive multifocal IOLs having multiple echelettes.

In typical reading or near vision conditions where the light is bright,the size of the pupil is small, e.g. between about 1 mm and 2 mm indiameter, and the eye has a large depth of focus (for example from apinhole effect), almost irrespective of the optics of the IOL. Largepupil size, e.g. larger than about 4-5 mm in diameter, generally appliesto low light conditions, and is often associated with distance visionfor which the power of the IOL is typically established. Therefore, manypatients would benefit most from an IOL that enhances the depth of focusin order to view at intermediate distances. An IOL having a singleechelette or ring effectively increases the depth of focus forintermediate pupil sizes, while maintaining the general increased depthof focus of small pupil sizes, and also maintaining an emphasis on farvision for large pupil sizes. At the same time, since the singleechelette and the remaining surface area of the optic or remaining lensportion (“non-echelette”) have unequal surface areas for almost allpupil sizes, there is an incomplete split between the foci. Since thesplit of light is incomplete, the separation of foci is incomplete. Thisincomplete separation of foci contributes to the extended depth of focusand the attenuation of dysphotopsia (e.g. halos).

FIG. 4A provides a graphical representation of a portion of a lensdiffractive profile according to embodiments of the present invention,which further explains a single microstructure embodiment. In FIG. 4A,the height of the surface relief profile (from a plane perpendicular tothe light rays) of each point on the echelette surface is plottedagainst the square of the radial distance (r² or φ from the optical axisof the lens. The echelette can have a characteristic optical zone 930and transition zone 931. Optical zone 930 can have a shape or downwardslope that may be linear when plotted against ρ as shown in FIG. 4A.When plotted against radius r, optical zone 930 can have a shape ordownward slope that is parabolic. As depicted here, central optical zone930 can provide a central parabolic echelette. An outer (refractive)zone can follow the base radius with a fixed offset. In some cases, theprofile can present an echelette or central portion 923 a and arefractive zone or peripheral portion 923 b.

As shown in FIG. 4A, transition zone 931 between the optical zone 930and the outer zone 933 can be sharp and discontinuous. Similarly, avertical transition between central portion or echelette 923 a andperipheral portion or refractive zone 923 b can be sharp anddiscontinuous. The height of the lens face sharply transitions fromsloping steadily downwards (e.g. across optical zone 930) to steppingvertically upwards (e.g. at transition zone 931), and the transitionsabruptly back to sloping steadily or substantially horizontal. In doingso, echelette 923 a or optical zone 930 also has a characteristic stepheight 932 defined by the distance between the lowest point and highestpoint of the echelette. Hence, the slope (or first derivative) and/orthe curvature (second derivative) of the diffractive surface arediscontinuous adjacent the transition. The first derivative can beindicated by the direction of the lines, and the second derivative canbe indicated by the curve of the line.

According to some embodiments, light comes from below, in the directionindicated by arrow A, and only hits the echelette 930 of the profile.According to some embodiments, in theoretical terms light does not hitthe vertical connection of the optical zone, and hence the profile canbe said to have no transition zone. According to some embodiments, inpractice when one attempts to produce such a profile, for instance bylathe cutting, it may be difficult to reproduce the sharp corner (e.g.at where the optical zone connects with the adjacent optical zone) andhence the corner may be rounded to some extent due to the finite chiselradius. Such rounding may have a negligible effect on the opticalperformance. According to related embodiments, transition zone 931,which can be referred to as the transition from the echelette to theadjacent zone or zones, can be shaped in a specific way, so as tooptimize the optical performance, for example, to minimize scatter froma sharp transition.

According to some embodiments, a central portion 923 a can be defined asan echelette, and a peripheral portion 923 b can be defined as arefractive zone.

FIG. 4B is a graphical representation of a diffractive profile 971 of alens, plotting the height of the surface relief profile at a particularpoint of an echelette 972 versus ρ, the square of the radius or distancedisplaced from a plane perpendicular to the light rays, and shown with aconventional diffractive profile 975, shown by the dotted line.According to some embodiments, an echelette can include an optical zoneor primary zone 977 and a transition zone 976. According to someembodiments, a central portion 972 a can be defined as an echelette, anda peripheral portion 972 b can be defined as a refractive zone.According to some embodiments, an echelette includes one primary zoneand one transition zone.

As shown in FIG. 4B, transition zone 976 between the echelette and theadjacent zone 978 may not be sharp and discontinuous. The height of thelens face can smoothly transition. In addition, echelette 972, orcentral portion 972 a, can have a characteristic profile height 974, andperipheral portion 972 b can have a characteristic profile height 974 adefined by the distance between the lowest point and height point of theechelette or portion. Hence FIG. 4B illustrates that the centralechelette may be of another shape, that there may be a transition zone,that the phase offset (height) at 974 a may be different from the phaseoffset (height) of the central zone 974, and that the outer orperipheral zone may have an alternative aspherical shape.

FIG. 4C is a graphical representation of a lens profiles, according toembodiments of the present invention disclosing a single echelettesurrounding a central refractive zone of the lens. The lens profileembodiment in FIG. 4C has one single echelette or microstructure 980 e,which is positioned as an annulus around a central refractive opticalzone 970 e. The annular echelette has an inner radius 982 e and an outerradius 984 e, a profile shape 986 e and a profile height 988 e(offset1). The annular echelette 980 e may be surrounded by a refractiveperipheral zone 990 e, having a profile height 998 e (offset2). Profileheights 988 e, 998 e may be characterized by their respective distancesfrom the base/central refractive zone. While it is not shown in FIG. 4C,it is noted that the refractive central and peripheral zones can beaspherical surfaces, designed to modify ocular aberrations, e.g.spherical aberration. A transition (e.g. vertical line) between amicrostructure and a refractive zone, as displayed in FIG. 4E may besharp or smooth, as further described elsewhere herein. In addition, therefractive zones may be spherical or aspherical, or mixed, having aspherical refractive zone and an aspherical refractive zone.

FIG. 4D provides a graphical representation of a cross section of asingle microstructure lens profile 200 on the posterior surface of alens with a ring diameter of 1.21 mm and a stepheight at 220 of 2.05 μm,corresponding with a phase delay of 0.5 lambda (see table 2). In thisexample, the ring diameter was reduced from 1.5 mm (which is the innerring diameter for a 2.0 Diopter conventional IOL diffractive lens) to1.21 mm by a scaling factor √2, as described in U.S. Pat. No. 5,121,980(Cohen). Only the inner portion and part of the outer portion of half ofthe lens is shown, although since the lens is rotationally symmetric,the other half is a mirror image. Profile 200 of the single ring surfaceincludes an inner portion 210 or single ring, a step or transition 220,and an outer portion 230. The outer portion 230 extends beyond thatdisclosed in FIG. 4D to 2.5 mm. Inner portion 210 extends between acentral location 270 of profile 200 and transition 220. Outer portion230 extends between transition 220 and a peripheral location (notshown).

The inner portion or echelette 210 includes a center 210 a and aperipheral edge 210 b. At center or central section 210 a of innerportion 210 where radial distance is zero, the sag (d) of inner portionis between the sag (d) of the diffractive base curve 240 and the sag (d)of the peripheral curve 260 at 1.03 μm from the peripheral curve 260,corresponding with a phase delay of 0.25 lambda (see table 2). Atperipheral edge 210 b, the sag (d) of inner portion 210 is substantiallyequivalent to the sag (d) of diffractive base curve 240 at 13.8 μm. Thevalue of sag (d) between radial distance zero and radial distance at theperipheral edge 210 b at 0.61 mm, gradually and smoothly changes from1.03 μm (at r=0) to the value of the base curve 240 (at r=0.61 mm) whichis 13.8 μm. This change occurs in a parabolic fashion. As shown here,inner portion can present a parabolic shape, for example as described inEquation 4a of Cohen, Applied Optics, 31:19, pp. 3750-3754 (1992),incorporated herein by reference.

At the peripheral edge 210 b where the radial distance (r) is 0.61 mm,the value of sag (d) steps or changes from the value of diffractive basecurve 240 to the value of peripheral curve 260. Where radial distance(r) corresponds to transition 220, sag (d) of inner portion isequivalent to the value of the diffractive base curve 240. Relatedly,the displacement of the profile approaches that of the diffractive basecurve as the radial distance increases from a value of zero to a valueof about 0.61 mm. The stepheight is 2.05 μm resulting in a phase delayof 0.5.

The outer portion 230 includes an inner or central edge 230 a and aperipheral edge (not shown). At inner edge 230 a, the sag (d) of outerportion is substantially equivalent to the sag (d) of peripheral curve260. At peripheral edge, the sag (d) of outer portion remainssubstantially equivalent to the sag (d) of peripheral curve 260. Thevalue of sag (d) for the outer portion of profile between radialdistance 0.61 mm and the peripheral portion at radial distance 2.5 mm isequivalent to the value of peripheral curve 260. The sag of the profileand the peripheral curve 260 are approximately equivalent between radialdistance values of 0.61 mm and 2.5 mm. Outer portion can provide anormal spherical or aspherical curve, such as a Tecnis aspheric surface,which corrects or treats the ocular spherical aberration.

Profile Parameters

The profile design can be characterized in terms of a set of parameters.Conventional multifocal lenses, having a plurality of echelettes, aretypically characterized by the parameters: add power and lightdistribution. For example, the single echelette of a profile can bedescribed as reflecting a lens add power and a light distribution (asdiscussed in more detail below). As discussed in previously incorporatedU.S. patent application Ser. Nos. 61/047,699 and 12/109,251, both filedApr. 24, 2008, lens add power can be based on the diameter or radialposition or location of a profile echelette, and light distribution canbe based on the relative height of an echelette.

Diffractive Power and Geometry of the Echelette

In conventional diffractive IOLs, the diameter (or size or width orsurface area) of the echelette is related to the diffractive power ofthe lens. As such, variations of the geometry of the single echelettedesign disclosed herein have been characterized according toconventional diffractive IOL design in terms of add power. Inparticular, the radius of the single echelette embodiments disclosedherein, are equivalent to the inner radius of conventional diffractiveIOLs with the same add power. As one skilled in the art knows, the addpower would not necessarily describe the optical characteristics of thesingle echelette embodiments disclosed herein. According to someembodiments, the diffractive power of the lens has a value within arange from about 0.5 diopters to about 3.0 diopters representing theechelette radius and diameter as detailed in Table 1 below. Table 1provides dimensions of various samples, where D represents the power indiopters, R represents the radius of the ring, or echelette, in mm, andDe represents the diameter of the ring in millimeters. In alternativeembodiments, the single echelette is an annulus around, or within, arefractive surface. In such case, a translation between diffractivepower and echelette size is represented by the surface area of theechelette. Table 1 provides dimensions for surface areas of theechelette.

TABLE 1 D R (mm) De (mm) Area (mm²) 0.5 1.48 3 6.9 1 1.05 2.1 3.5 1.50.86 1.7 2.3 2 0.74 1.5 1.7 2.5 0.66 1.3 1.4 3 0.61 1.2 1.2

Phase Delay and Geometry of the Echelette

The step height or profile height can determine the phase delay or phaseshifting profile. A greater step height can correspond to a greaterphase shift. In conventional diffractive IOLs, the phase shift isrelated to the light distribution of the lens. As such, variations ofthe geometry of the single echelette design disclosed herein have beencharacterized according to conventional diffractive IOL design in termsof light distribution. As one skilled in the art knows, the lightdistribution would not necessarily describe the optical characteristicsof the single echelette embodiments disclosed herein. According to someembodiments, a lens can include a transition characterized by a stepheight producing a phase shift between about 0.25 and about 1 times thedesign wavelength. In some cases, a diffractive profile can becharacterized by a design wavelength, and the lens can include atransition characterized by a step height producing a phase shiftbetween about 0.15 and about 2 times the design wavelength.

According to some embodiments the lens may include a transitioncharacterized by a step height producing a phase shift of about 0.5. Inother embodiments, the lens may include a transition characterized by astep height of about 0.4.

In terms of an echelette transition, the sag at the transition increasesan amount equal to the offset value. Table 2 below provides dimensionsof various samples disclosing the relationship between phase delay (inwavelengths) and step height (in μm), as valid for an example IOLmaterial.

TABLE 2 Phase Delay Stepheight 0.896 3.68 0.700 2.87 0.590 2.42 0.5092.09 0.500 2.05 0.423 1.74 0.366 1.50 0.350 1.44 0.250 1.03 0.150 0.62

Thus, in an exemplary embodiment where the lens has a power of 2.5D witha 0.423 phase shift according to the design disclosed in FIG. 4, theradius of the single ring would be 0.66 mm and the stepheight would be1.74 μm.

Pupil Dependence

In an exemplary embodiment, the single ring central or single centralechelette design has an optical performance that depends on the pupilsize. For very small pupils, where the pupil is smaller than the size ofthe central echelette, the echelette will act as a refractive lens,having a very large depth of focus, due to the pinhole effect. Forhigher and medium pupil sizes, where the pupil covers the centralechelette and a part of the outer zone, the lens will act as adiffractive/refractive lens, with an appropriate phase shift. The sizeof the central echelette influences the pupil dependence of the lens. Assuch, the size of the central echelette can be chosen, depending on thepupil sizes of a specific patient. For example, the pupil sizes of apatient may be measured in bright light, in dim light, during far visionand during near vision, and in the different combinations of light leveland accommodative effort. These different pupil sizes, which may bedefined as pupil dynamics, can be used as input parameters for anoptimal design of the single ring or single echelette design.

For example, if a patient has a pupil diameter during near vision (e.g.viewing target at close distance, with high accommodative effort)smaller than 2 mm, having this pupil dimension with both bright and dimlight, then the size of the central echelette may be selected to besmaller than 2 mm (e.g. outer diameter of the circular echelette of FIG.4A), as to provide adequate near and/or intermediate vision. Relatedly,if a patient has a pupil diameter during near vision larger than 2 mm,having this pupil dimension with both bright and dim light, then thesize of the central echelette may chosen 2 mm or larger, as to provideadequate near and intermediate vision. In general, the diameter of thecentral echelette can be smaller than the smallest pupil size thepatient has under any condition (e.g. bright/dim light; near/farvision). For any type of pupil dynamics, the size, the profile, and theoffsets may be chosen to maximize the lens performance for that specificpatient, or group of patients. Generally, this is a trade off betweenthe different vision circumstances (combinations of light level andaccommodative effort) at which the pupil of the patient is measured.Accordingly, exemplary embodiments include a method of designing anophthalmic lens comprised of utilizing pupil size measurements and basedon the measurements determining the size of an isolated echelette toimpose on the surface of a lens. The pupil size measurements may bebased on a group of patients.

Evaluation of Variations of a Specific Example

With regard to the example as shown in FIG. 4A, a number of variationshave been analyzed. In these examples, the central echelette has beenvaried in size, and step height (offset). As such, variations of theechelette design have been characterized according to conventionaldiffractive IOL design in terms xD/y %, where xD represents the addpower that the echelette design represents (e.g. based on echelette sizeand/or position, and step height), and y % represents the portion of thelight directed into the first order focus. The add power and lightdistribution are being used herein to characterize the geometry of thecentral echelette. In particular, the radius of the single echeletteembodiments disclosed herein, are equivalent to the inner radius ofconventional diffractive IOLs with the same add power. Analogously, thestep height and associated phase delay of the single echeletteembodiments disclosed herein are equivalent to the step height/phasedelay of conventional diffractive IOLs with the same light distribution.As one skilled in the art knows, the add power and light distributionwould not describe the optical characteristics of the single echeletteembodiments as disclosed herein.

Table 3 discloses the relationship between percentage of light betweennear and far focus, phase delay, and stepheight for the IOL material inthe example.

TABLE 3 Percent Near Phase Delay Stepheight 99 0.896 3.68 85 0.700 2.8768 0.590 2.42 52 0.509 2.09 50 0.500 2.05   35% 0.423 1.74 25 0.366 1.5023 0.350 1.44 10 0.250 1.03  3 0.150 0.62

For example, a 2D/35% echelette design represents a lens with a centralechelette with a radius of 0.74, wherein the phase delay is 0.423 andthe stepheight is 1.74. Similar nomenclature is used in conjunction withthe designs as analyzed in FIGS. 6-20 herein.

FIG. 5 illustrates an optical system layout 300 of a schematic eye thatincludes a spectacle lens 310, a cornea 320, an intraocular lens 330,and a retina 340. The cornea 320 has the spherical aberration of anaverage cataract patient. The schematic eye also has the averagechromatic aberration of the human eye. This so called ACE model, oraverage cornea eye model, is based on actual wavefront measurementscollected from a sampling of cataract patients, and chromatic aberrationand dispersion of the human eye. The eye model is substantiallydescribed in: Norrby, S., Piers, P., Campbell, C., & van der Mooren, M.(2007) Model eyes for evaluation of intraocular lenses. Appl Opt, 46(26), 6595-6605, the content of which is incorporated herein byreference. Using the ACE model, it is possible to evaluate various lensprofiles. By changing the power of the spectacle lens, it is possible togenerate various defocus curves. For example, a negative power spectaclelens can mimic the effect of looking at an object at a close distance.

With regard to the example as shown in FIG. 4A, a number of variationshave been analyzed, and the image quality versus defocus has beencalculated in the ACE eye model. In order to present information aboutpupil dependent performance of the example designs, the image analysisis carried out for pupil diameters of 2.0 mm, 3.0 mm, and 4.0 mm. Thisis depicted in FIGS. 6A to 9D, and FIGS. 10A to 13C. Hence, FIGS. 6A to9D and FIGS. 10A to 13C can be considered as a single set. In thisseries, the size of the echelette is being varied from 1.2 mm to 3.0 mmin diameter, and the step height is being varied from 0.6 to 3.7 μm. Theechelette geometry in this series is characterized in terms xD/y %. Thegeneral lens configuration was an equi-biconvex optic, having anaspherical anterior surface and a spherical posterior surface. Thesingle ring design was applied onto the posterior surface.

FIGS. 5A-5C can serve as a reference. FIG. 5A shows a regular asphericaldesign, correcting the corneal spherical aberration. FIG. 5B shows aregular spherical design. FIG. 5C shows a regular diffractive multifocaldesign, having a 4-diopter add power. It should be noted that thediffractive multifocal IOL of FIG. 5C has a second peak, that is notshown, as it is outside the horizontal scale of the graph. The secondpeak is similar to the first peak in shape, height, and width.

The horizontal (x-) axis denotes the amount of defocus, expressed indiopters of spectacle power. The left half of the figures, correspondingto minus spectacle powers, represent the situation in which thespectacle makes the eye myopic. The right half of the figure,corresponding to positive spectacle power, represents the situation inwhich the spectacle makes the eye hyperopic. The vertical (y-) axisdenotes image quality, presented by the volume under the white-light MTFcurve, as a percentage of the volume under the white-light diffractionlimited MTF. As such, it is used as a measure of retinal image quality.The left part of the figure represents the image quality for near andintermediate vision, corresponding to spectacle powers up to −2.5D.

As illustrated FIGS. 6A, 7A, 8A, and 9A, an echelette designrepresenting a 0.5D add may provide little benefit over a regularmonofocal lens. Other designs indicate some benefit by having anextended depth of focus for at least some of the pupil sizes. None ofthe single echelette designs, although their echelette is designed ashaving an add power, show two fully separated peaks (with zero MTFVolume in-between the peaks), such as for the multifocal IOL shown inFIG. 5C. Many designs, although their echelette is designed as having anadd power, do not show two separate peaks in the defocus curve, as wouldbe typical for multifocal designs. For example, FIGS. 12A, 13A, 13B, and13C, while having an increased depth of focus, that is, the volume underthe white-light MTF curve is larger than zero for an increased range ofdefocus values, demonstrate a continuous decreasing image quality whenchanging the defocus from zero diopter to −2.5D. Other options show atendency toward this behavior, having only a very limited dip in theimage quality between the peaks representing zero and first order focus,for example those referenced in FIGS. 10A, 11A-C, and 12B-C. For theseexamples, this small dip in image quality is only present for thesmaller pupil size (2.0 mm). Some options demonstrate an image qualityin far vision that is independent of pupil size, for example thosereferenced in FIGS. 8D, 9D, 10A-C, and 11A-C.

FIGS. 14A to 17C illustrate further evaluations of the profile designsreferenced in FIGS. 10A to 12C, in a computer model of a “physical eye”of an actual patient. This computer model incorporates optical higherorder aberrations from the cornea of the patient. The methodology of theeye model is described in: Piers, P. A., Weeber, H. A., Artal, P. &Norrby, S. “Theoretical comparison of aberration-correcting customizedand aspheric intraocular lenses” J Refract Surg 23, 374-84 (2007), thecontent of which is incorporated herein by reference. The “physical eye”model is associated with a better prediction of the optical performanceof IOL designs in the patient.

The profile designs involve a single ring diffractive lens according toembodiments of the present invention. These graphical illustrationsdepict characteristics of image quality associated with defocus curves.FIGS. 14A to 17C can be described as one set. In this series, the sizeof the echelette is being varied from about 1.2 mm to 1.5 mm indiameter, and the step height is being varied from 0.6 to 1.7 μm. Theechelette geometry in this series is characterized in terms xD/y %. Thegeneral lens configuration was an equi-biconvex optic, having a Tecnisaspherical anterior surface and a spherical posterior surface. Thesingle ring design was applied onto the posterior surface. The designprofiles were assessed for a 2 mm pupil, a 3 mm pupil, and a 4 mm pupil.FIGS. 18A through 18C can be described as the reference.

FIG. 18A shows a regular aspherical design, correcting the cornealspherical aberration. The evaluation of this design profile is assessedfor a 2 mm pupil, a 3 mm pupil, and a 4 mm pupil. FIG. 18B shows aregular spherical design. The evaluation of this spherical IOL designprofile is assessed for a 2 mm pupil, a 3 mm pupil, and a 4 mm pupil.FIG. 18C can be characterized as a diffractive multifocal+4D, similar tothat described in FIG. 5C.

According to some embodiments, general trends as seen in the ACE modelare also valid in the physical eye model. Many designs exhibit anextended depth of focus, when compared to the regular monofocal IOLs.Where there is a dip in the image quality between the far and nearfocus, for example at FIG. 10A versus FIG. 14A, FIG. 11A versus FIG.15A, FIG. 11B versus FIG. 15B, FIG. 11C versus FIG. 15C, FIG. 12B versusFIG. 16B, and FIG. 12C versus FIG. 16C, the magnitude of this dip isreduced. The results indicate that these options deliver a certain imagequality over a range of distances, without dropping significantly atsome intermediate distance.

As illustrated in the figures, a lens may provide an MTF volume of atleast about 35% throughout a range from about −1.25 to about 0.25 for a2.0 mm pupil. In other words, a lens can provide an MTF volume of atleast 35% over a continuous range of at least about 1.5D for a 2.0 mmpupil. Certain embodiments of the present invention provide for an MTFvolume of at least 35% over a continuous range of at least about 0.75D.Other embodiments can provide an MTF volume of at least 35% over acontinuous range of at least about 1.0D. More preferably, embodimentscan provide an MTF volume of at least 35% over a continuous range of atleast 1.25D.

FIGS. 19A and 19B show measured defocus curves of samples pertaining toa 3 mm pupil (FIG. 19A) and a 5 mm pupil (FIG. 19B). These samplescorrespond to single ring IOL, or single ring echelette, similar to thatdescribed in FIGS. 21 and 22. The horizontal axis denotes the defocusvalue in the spectacle plane, in diopters. The vertical axis denotes themodulus (MTF) at 50 cycles per millimeter. The graphs demonstrate thatthe actual lenses, as made according to the respective designs, exhibitthe extension of the depth of focus at minus defocus values. Asillustrated in the figures, a lens may provide an MTF at 50 cycles permillimeter of at least about 15 throughout a range from about −1.0 toabout 0.5 for a 3.0 mm pupil. In other words, a lens can provide an MTFat 50 cycles per millimeter of at least 15 over a continuous range of atleast about 1.5D for a 3.0 mm pupil. Certain embodiments provide an MTFat 50 cycles per millimeter of at least 15 over a continuous range of atleast 1.0D.

FIGS. 20A-20C show measured defocus curves in the ACE eye model of anexemplary embodiment disclosed in section 4 with a ring diameter of 1.21mm and a phase delay of ½ wavelength. The horizontal axis denotes thedefocus value in the spectacle plane, in diopters. The vertical axisdenotes the modulus (MTF) at 100 cycles per millimeter. Data for 3 mm, 4mm, and 5 mm pupil diameters are included. As illustrated in thefigures, a lens may provide an MTF at 100 cycles per millimeter of atleast about 7 throughout a range from about −1.0 to about 0.8 for a 3.0mm pupil. In other words, a lens can provide an MTF at 100 cycles permillimeter of at least 7 over a continuous range of at least about 1.8Dfor a 3.0 mm pupil. Certain embodiments provide an MTF at 100 cycles permillimeter of at least 7 over a continuous range of at least 1.5D. Thegraphs demonstrate that the actual lenses, as made according to therespective designs, exhibit the extension of the depth of focus.

FIG. 21 shows an exemplary diffractive single ring IOL wherein thegeometry is characterized by a 1.0D/100% design profile. FIG. 22 showsan exemplary diffractive single ring IOL wherein the geometry ischaracterized by a 2.0D/10% design profile.

The term single microstructure can refer to the fact that, when viewedmacroscopically, for example as shown in FIGS. 21-22, just one singlering is visible on the surface. In other words, there is one opticalphase transition on the whole optical surface. Optionally, the termsingle microstructure can refer to the fact that the lens has only onesingle echelette, represented by the inner portion of the lens surface.In alternative embodiments, the single echelette is an annulus around acentral portion of the lens. An annulus echelette can have two phasetransitions, one at the inner radius of the echelette, and one at theouter radius of the echelette.

IOLs such as the exemplary embodiments depicted in FIGS. 21-22 can bemade of an acrylic material. An echelette can be placed on the posterioror anterior surface, and the peripheral zone may be aspherical. Theopposing surface may be aspherical (e.g. correcting corneal sphericalaberration).

Table 4 below provides dimensions of various samples, where Derepresents the diameter of the ring, or echelette, in millimeters, andstepheight represents the height of the profile, in μm. As in Table 3above, the single echelette design geometry is characterized in terms ofconventional diffractive IOL nomenclature regarding add power andpercentage of light.

The lenses were tested in the ACE model, using white light.

TABLE 4 Name De (mm) step height (μm) 1.0D/100% 2.10 3.7 1.5D/30% 1.711.7 2.0D/30% 1.48 1.7 2.0D/10% 1.48 1.0

FIGS. 23A-1 to 23D-2 and 24 show measured performance of dysphotopsia(e.g. halo effects) of samples for a 4.0 mm pupil, in an ACE eye model.These figures are based on the image of an extended light source ofwhite light, representing the headlight of a car at a distance of about50 meters, and correspond to IOL samples, or measurements on reallenses. FIG. 23A-1 shows the image generated by the light source,illustrating the appearance of the halo of a 2.0D/30% design. FIG. 23B-1shows the image of an aspherical monofocal. FIG. 23C-1 shown the imageof a refractive bifocal lens with a +1D add power. FIG. 23D-1 shows theimage of a diffractive multifocal lens with a 4D add power. Thesefigures demonstrate that the amount of halo of the 2.0D/30% design, asshown in FIG. 23A-1, is reduced as compared to a diffractive multifocallens as shown in FIG. 23D-1, and as compared with a refractive bifocallens with 1D add power as shown in FIG. 23C-1. FIGS. 23A-2, 23B-2,23C-2, and 23D-2 provide negative images of FIGS. 23A-1, 23B-1, 23C-1,and 23D-1, respectively, for better visibility.

FIG. 24 shows a graphical representation of the measured light scatter(straylight) corresponding to the light source images of FIGS. 23A-1,23B-1, 23C-1, and 23D-1. The horizontal axis denotes the visual angle,in degrees, and the vertical axis denotes the amount of scatter,represented by the scatter parameter. The scatter parameter is definedas the logarithm of the light energy times the square of the visualangle. The size of the halo, as shown in FIGS. 37A-1, 37B-1, 37C-1, and37D-1 in the straylight graph of FIG. 24 is between zero and about 0.5degrees. The peak is part of the halo. In other words, pure straylightis measured for visual angles above 0.5 degrees. The vertical axis hasarbitrary units. FIG. 24 shows the straylight of the 1.5D/30% design(line 23A), the 2.0D/30% design (line 23B), and the 2.0D/10% design(line 23C). The amount of straylight is substantially the same for thesethree designs. For reference FIG. 24 also shows the straylight imagecorresponding to an aspherical monofocal (line 23D), as well as arefractive bifocal lens with a +1D add power (line 23E), and adiffractive multifocal lens with a 4D add power (line 23F). FIG. 24shows that the amount of straylight of the 3 designs having a singleechelette is smaller than that of the diffractive multifocal lens, andjust slightly higher than that of a regular monofocal lens. FIG. 24 alsoconfirms the conclusion from FIGS. 23A-1 to 23D-2 that a design having asingle echelette does not produce any significant halos.

While the examples above describe a parabolic echelette, an echeletteand outer zone design may be configured so as to reduce the amount oflight in predetermined non-functional diffractive orders. Additionalaspects of these features are described in previously incorporated U.S.patent application Ser. No. 12/429,155 filed Apr. 23, 2009. Using thesame principles as set forth in the aforementioned application, theamount of light in other diffractive orders can be enhanced, as to aidviewing using those diffractive orders.

Embodiments of the present invention may be combined with a multifocallens design, and with that extend the depth of focus of each focus ofthe multifocal lens. Similarly, embodiments of the present invention maybe combined with an accommodating lens design, by which the range ofaccommodation of the accommodating lens can be extended. In addition,embodiments of the present invention may be combined with lensescorrecting ocular aberrations, like toric lenses, aspherical lenses,lenses correcting chromatic aberrations, and the like. Embodiments forcorrecting chromatic aberrations may, for example, increase the phasedelay of the echelettes by a discrete multiple of wavelengths. Forexample, in the preceding example in which a phase delay of 0.5 wasused, corresponding to a stepheight of 2.05 μm, an alternativeembodiment may have a phase delay of 1.5, corresponding to a stepheightof 6.15 μm. This embodiment thus directs the first order diffraction tothe far focus, and the second order diffraction establishes the depth offocus at the intermediate and near range.

While the exemplary embodiments have been described in some detail, byway of example and for clarity of understanding, those of skill in theart will recognize that a variety of modification, adaptations, andchanges may be employed. Hence, the scope of the claims should not belimited to the description of the preferred versions contained herein.

What is claimed is:
 1. An ophthalmic lens comprising: an anterior faceand a posterior face, the faces disposed about an optical axis; and acentral echelette imposed on the anterior or the posterior face.
 2. Theophthalmic lens of claim 1, wherein the anterior and/or posterior facehas a diffractive profile.
 3. The ophthalmic lens of claim 1, whereinthe anterior and/or posterior face has a toric profile.
 4. Theophthalmic lens of claim 1, wherein the echelette is disposed within acentral zone of the lens.
 5. The ophthalmic lens of claim 1, wherein theechelette is disposed within an annular ring surrounding a centralrefractive zone of the lens.
 6. The ophthalmic lens of claim 5, whereinthe lens comprises a peripheral zone that surrounds the annular ring. 7.The ophthalmic lens of claim 1, wherein the echelette is characterizedby a constant phase shift.
 8. The ophthalmic lens of claim 1, whereinthe echelette is characterized by a surface area between 1 and 7 squaremillimeters.
 9. The ophthalmic lens of claim 8, wherein the echelettehas a diameter within a range from about 1 mm to about 5 mm.
 10. Theophthalmic lens of claim 1 wherein the echelette is characterized by aparabolic curve.
 11. The ophthalmic lens of claim 1, wherein the lensfurther comprises a peripheral portion characterized by a sphericalcurve or an aspherical curve.
 12. The ophthalmic lens of claim 12,wherein the peripheral portion has a refractive profile.
 13. Theophthalmic lens of claim 1, wherein the ophthalmic lens furthercomprises a transition characterized by a step height having a valuewithin a range from about 0.5 μm and about 4 μm.
 14. The ophthalmic lensof claim 13, wherein the step height provides a phase shift betweenabout 0.25 and about 3 times the design wavelength.
 15. The ophthalmiclens of claim 1, wherein the lens provides an MTF volume of at least 35%over a range of at least about 0.75D.